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authorHugh Dickins <hughd@google.com>2017-01-07 15:37:31 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-01-07 17:49:33 -0800
commitb0b9b3df27d100a975b4e8818f35382b64a5e35c (patch)
tree8d900d2be3801a7dd10c86c594b37e421167392c /mm
parent87bc610730a944b49f1c53ab9f4230d85f35df0c (diff)
mm: stop leaking PageTables
4.10-rc loadtest (even on x86, and even without THPCache) fails with "fork: Cannot allocate memory" or some such; and /proc/meminfo shows PageTables growing. Commit 953c66c2b22a ("mm: THP page cache support for ppc64") that got merged in rc1 removed the freeing of an unused preallocated pagetable after do_fault_around() has called map_pages(). This is usually a good optimization, so that the followup doesn't have to reallocate one; but it's not sufficient to shift the freeing into alloc_set_pte(), since there are failure cases (most commonly VM_FAULT_RETRY) which never reach finish_fault(). Check and free it at the outer level in do_fault(), then we don't need to worry in alloc_set_pte(), and can restore that to how it was (I cannot find any reason to pte_free() under lock as it was doing). And fix a separate pagetable leak, or crash, introduced by the same change, that could only show up on some ppc64: why does do_set_pmd()'s failure case attempt to withdraw a pagetable when it never deposited one, at the same time overwriting (so leaking) the vmf->prealloc_pte? Residue of an earlier implementation, perhaps? Delete it. Fixes: 953c66c2b22a ("mm: THP page cache support for ppc64") Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Michael Neuling <mikey@neuling.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Balbir Singh <bsingharora@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Hugh Dickins <hughd@google.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/memory.c47
1 files changed, 20 insertions, 27 deletions
diff --git a/mm/memory.c b/mm/memory.c
index 7d23b5050248..9f2c15cdb32c 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3008,13 +3008,6 @@ static int do_set_pmd(struct vm_fault *vmf, struct page *page)
ret = 0;
count_vm_event(THP_FILE_MAPPED);
out:
- /*
- * If we are going to fallback to pte mapping, do a
- * withdraw with pmd lock held.
- */
- if (arch_needs_pgtable_deposit() && ret == VM_FAULT_FALLBACK)
- vmf->prealloc_pte = pgtable_trans_huge_withdraw(vma->vm_mm,
- vmf->pmd);
spin_unlock(vmf->ptl);
return ret;
}
@@ -3055,20 +3048,18 @@ int alloc_set_pte(struct vm_fault *vmf, struct mem_cgroup *memcg,
ret = do_set_pmd(vmf, page);
if (ret != VM_FAULT_FALLBACK)
- goto fault_handled;
+ return ret;
}
if (!vmf->pte) {
ret = pte_alloc_one_map(vmf);
if (ret)
- goto fault_handled;
+ return ret;
}
/* Re-check under ptl */
- if (unlikely(!pte_none(*vmf->pte))) {
- ret = VM_FAULT_NOPAGE;
- goto fault_handled;
- }
+ if (unlikely(!pte_none(*vmf->pte)))
+ return VM_FAULT_NOPAGE;
flush_icache_page(vma, page);
entry = mk_pte(page, vma->vm_page_prot);
@@ -3088,15 +3079,8 @@ int alloc_set_pte(struct vm_fault *vmf, struct mem_cgroup *memcg,
/* no need to invalidate: a not-present page won't be cached */
update_mmu_cache(vma, vmf->address, vmf->pte);
- ret = 0;
-fault_handled:
- /* preallocated pagetable is unused: free it */
- if (vmf->prealloc_pte) {
- pte_free(vmf->vma->vm_mm, vmf->prealloc_pte);
- vmf->prealloc_pte = 0;
- }
- return ret;
+ return 0;
}
@@ -3360,15 +3344,24 @@ static int do_shared_fault(struct vm_fault *vmf)
static int do_fault(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
+ int ret;
/* The VMA was not fully populated on mmap() or missing VM_DONTEXPAND */
if (!vma->vm_ops->fault)
- return VM_FAULT_SIGBUS;
- if (!(vmf->flags & FAULT_FLAG_WRITE))
- return do_read_fault(vmf);
- if (!(vma->vm_flags & VM_SHARED))
- return do_cow_fault(vmf);
- return do_shared_fault(vmf);
+ ret = VM_FAULT_SIGBUS;
+ else if (!(vmf->flags & FAULT_FLAG_WRITE))
+ ret = do_read_fault(vmf);
+ else if (!(vma->vm_flags & VM_SHARED))
+ ret = do_cow_fault(vmf);
+ else
+ ret = do_shared_fault(vmf);
+
+ /* preallocated pagetable is unused: free it */
+ if (vmf->prealloc_pte) {
+ pte_free(vma->vm_mm, vmf->prealloc_pte);
+ vmf->prealloc_pte = 0;
+ }
+ return ret;
}
static int numa_migrate_prep(struct page *page, struct vm_area_struct *vma,